Automatic defrost control



Feb, 2, 1954 c. S. GRIMSHAW AUTOMATIC DEFROST CONTROL Filed Dec. 19, 1951 blk] H i5 Attovhe'.

Patented Feb. 2, 1954 AUTOMATIC DEFROST CONTROL Charles S. Grimshaw, Erie, Pa., assignor to General Electric Company, a corporation of New York Application December 19, 1951, Serial No. 262,446

12 Claims.

My invention relates to deirosting apparatus and more particularly to controls for automatically eiecting deirosting of refrigerator evaporators.

In many household refrigerators, the evaporator for cooling the food storage compartment is exposed to the air in this compartment. Since the evaporator is at a colder temperature than the air and below the freezing point oi Water, moisture condenses on the evaporator and forms as frost. Ultimately, in order to maintain the desired operating eiliciency oi the evaporator, it is necessary to remove this insulating layer of frost. Since the removal oi this frost manually is a somewhat distasteful and time-consuming task, it is desirable to provide some automatic means for eiiecting the deirosting of the evaporator at intervals.

Accordingly, it is an object oi my invention to provide an improved control for automatically effecting defrosting of an evaporator.

It is another object or my invention to provide an improved control for automatically introducing an additional opposing force for defrosting.

It is a further object of my invention to provide an improved arrangement for starting refrigeration at the expiration of the deirosting period.

It is still another object of my invention to provide a control including an improved arrangement for obtaining a defrost temperature setting which is independent of changes in the normal temperature setting.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out With particularity in the claims annexed to and forming part of this specification.

In carrying out the objects of my invention, an interfering member is provided for acting as a stop, opposing movement of an operating arm of the control to the refrigeration-starting position when deirostirxy is to be accomplished. The position of this member is controlled by a rotatable cam which is periodically advanced during normal operation of the control. The member prevents movement of the operating arm to the refrigeration-starting position until a greater than normal expansion of the temperature- 'esponsive device oi the control has occurred, that is until the temperature of the evaporator has reached a predetermined abnormally high temperature. This additional expansion of the temperature-responsive element is opposed by a defrost spring. When the abnormally high temperature has been reached, a trip arm, movable by the temperature-responsive element, eiects a shifting of the interfering member to remove the opposition of this member to movement of the operating arm of the control to the refrigeration-starting position. In one form of my invention a toggle member is employed as the interfering member and the trip arm is arranged to effect a breaking of the toggle member to terminate the deirosting period.

For a better understanding of my invention reference may be had to the accompanying drawing in which Fig. l is a View, partly in section, oi a control device incorporating an embodiment of my invention during normal operation of the refrigerating system; Fig. 2 is a View on a slightly reduced scale of the apparatus of Fig. l in the defrosting position; Fig. 3 is a view of a portion oi the control of the end of the defrosting period; Fig. 4 is another View of the control shortly after the termination of the deirosting period; and Fig. 5 is a detail View of a modiiication of the invention.

Referring to the drawing, the control is shown as applied to controlling the position of a valve l for governing flow of refrigerant from a conduit 2 to a conduit 3. Refrigerant is supplied through conduit 3 to an evaporator or other cooling unit (not shown). The valve i includes a valve plunger 4 adapted to engage a valve seat 5. A magnet e is secured to the upper end of the plunger, and the position oi this magnet and or the plunger is controlled by a movable yoke l acting on the magnet. While in the specific illustration, the control has been shown acting to control the position oi the valve for governing the flow of refrigerant to an evaporator or other cooling unit, it will be apparent as the following description proceeds that this control can equally well be employed for opening and closing contacts to stop and start a refrigerating unit in the conventional manner employed in such controls.

The valve-controlling yoke l is mounted on one end of a two-part operating arm i?. This operating arm 8 includes a iirst part or element 8 and. a second part or element It. These parts are related by a hairpin spring II, knife edges l2 and I3 of these parts of the arm S engaging opposite sides of the hairpin spring il. This construction of the operating arm 8 including the hairpin spring Il is employed to secure snap action operation in a manner well known in the art. The rlrst part 9 of the operating arm 8 is s pivotally mounted between upstanding projections Iii secured to the housing I of the control. The second part It of the operating arm 8 is supported from a depending bracket It which is secured a rivet il or other suitable fastening device to a wall of the housing I5. The part it is connected to the bracket I6 by a flat resilient strin IS which affords the necessary movement of the part IG of the operating arm 8. The resilient strip I8 is secured by rivets I9 or other suitable fastening devices to the bracket I'S and to the part iii of the operating arm-Ei.

In order to eiect movement of the operating arm 8 between one position for opening the valve to start refrigeration and a second position for closing the valve to stop refrigeration, a temperature-responsive element or bellows 2@ is mounted on the housing i5. The bellows is connected by a tube 2i to a thermostatie bulb (not shownl positioned to be responsive to the temperature of the evaporator. The operating arm 8 is biased by a spring 22 which engages the part 9 of the operating arm 2,. A cap 23 is provided forthe upper end of the spring 22 and an adjusting screw 24 threaded into the wall of the housing i5 engages the cap 23 for varying the biasing force exerted by the spring 22. The part 9 of the operating arm B includes anupwardly extending boss .25 for assisting in positioning the lower end of the spring 22.

Under normal operating conditions, that is during normal cycling of the refrigerating system, the movement of the operating arm 3 and hence the position of the valve I, is controlled by the expansionand contraction of the bellows 2li under the biasing force of the opposing spring 22. For example, in the position of the apparatus shown in Fig. l, the yoke 'l is in its lower position, attracting the magnet 6 upwardly and lifting the valve plunger 4 to supply refrigerant to the evaporator. As the temperature o the evaporator is lowered, the bellows 20 contracts and the part 9 of the operating arm 8 is moved downwardly by the spring 22. This eiects a downward movement of the knife edge I2, eventually bringing this knife edge I2 below a line extendthrough the knife edge I3 and the pivot point of the part I0 of the arm 8. Then, through the action of the hairpin spring Il, a snap action upward movement of the part IQ of the operating arm 8 is eiected. This shifts the yoke 'I to the upper position corresponding to that shown in Fig. 2, attracting the magnet downwardly to close the valve and discontinue supply of refrigerant. Conversely as the evaporator then warms to a predetermined maximum temperature, the bellows 2i) expands and acts through the interposed trip arm 25 to raise the part 9 of the operating arm 8, eiiecting a snap action movement of the yoke i to the position shown in Fig. 1, thereby opening the valve I.

During normal operation, the control cycles between the refrigeration-starting and refrigeration-stopping positions in the manner described above. After a number of such cycles over a period of time, frost builds up on the evaporator to a sufficient extent to have an adverse effect on the eiciency of the evaporator in effecting cooling of the air in which it is disposed. In accordance with my invention7 after a predetermined number of such normal cycles of the control, the control is automatically positioned for effecting a temporary abnormally high temperature of the evaporator suicient to insure melting of all frost from the evaporator. In order to 113,39@

such defrosting, a toggle member or stop 21 is provided for opposing downward movement of the part lil of the operating arm 8 until the evaporator has reached the predetermined abnormally high temperature. rThe position of the toggle member or interfering member 2l is controlled by a rotatable disk or cam 2S. This cam 28 is periodically advanced by the cycling of the control during normal operation. Speciiically, a depending pawl 2S, which may be mounted on the part 9 of the operating arm 8 by a rivet or other suitable fastening device 3@ or which may be formed integrally with part 9 is arranged to engage a ratchet wheel or ratchet 3 I. The ratchet wheel 3i is connected through gears 32 and 33 to rotate the cam 2t. The ratchet wheel 3l, the gears 32 and 33 and the cam 28 are all rotatably mounted on supports or brackets, one of which is shown at 34, extending upwardly from the base of the housing It. lt can be seen that each time the part S of the operating arm t is moved upwardly at the start of a refrigerating cycle, the pawl 29, engaging the teeth of the ratchet wheel 3l, moves the ratchet wheel in a clockwise direction. The teeth on the ratchet wheel are chosen so that the normal upward movement of the pawl 29 advances the ratchet wheel by the amount of one tooth. Reverse rotation of the ratchet wheel 3| during the downward movement of the part 9 of the operating arm 8 at the end of the refrigerating portion of the operating cycle is prevented by a xed resilient strip or pawl v35 which is secured to or formed integral with one of the supports '315i and which engages the teeth of the ratchet wheel 3i.

The toggle member 2l includes two pivoted elements 36 and 3l. These pivoted elements 36 and 3l are pivotally connected at the knuckle 33 of the toggle member. The pivoted element 36 of the toggle member is of channel shape and includes an upper knife edge 39 adapted to engage a depending flange lil of the part i@ ci 'the operating arm 8 under defrosting conditions. The lower end of the base of the channel section of the pivoted element 3S is bent out to form a tongue 4I adapted to engage the periphery or surface 42 of the rotatable disk or cam 28. The lower pivoted element 3'! of the toggle member 2 is formed from an elongated rod, bent to provide a loop'portion I3 received within a slot fill in a support 45 at the base of the housing I5. The loop portion i3 is retained within the slot 134i by a closure element tit which blocks the opening of the slot 44. The pivoted element 3l' further includes a rearwardly extending horizontal portion adapted to pass through openings in the channel-shaped upper pivoted element 35 at the knuckle 38. The element 3l further includes a forwardly extending end portion el? which is adapted to engage the pivoted element C36 to limit the counterclockwise rotation of this pivoted element 36. The toggle member 2'! and specically the tongue BI of the upper pivoted elcment 36 thereof is biased into engagement with the periphery i2 of the cam 23 by a spring 48. One end of the spring llt is secured to upwardly extending ea1 49 mounted on the base of the housing i5 and the other end of the spring is secured in an opening in the pivoted element 3S of the toggle member 2l.

During normal operation of the reirigerating system, the toggle member 2i' occupies the position shown in Fig. 1, being heid in this position against the bias of the spring ts by the engagemem Of the tongue 4I with the periphery 42 of 5 the cam 28. The cam 28 includes a recess 5| in its periphery or surface 42. As ratchet wheel 3| is periodically advanced during the normal cycling of the control, the cam 28 is rotated in a counterclockwise direction, as indicated by the arrow, and the recess 5| is progressively moved toward alignment with the tongue 4| of the toggle member 21. When the recess 5| reaches alignment with the tongue 4|, the tongue 4| passes into the recess 5| under the influence of the biasing spring 48, and the toggle member 21 is then moved into the position shown in Fig. 2. n the position shown in Fig. 2, the knife edge 39 is positioned to engage the lower tip of the ange 4B and thereby to oppose downward movement of the part |8 of the operating arm 8 to the lower position in which the valve is opened and refrigeration is started. The construction of the toggle member 21 is such that in the position shown in Fig. 2, the knuckle 3S thereof is to the right of a line extending between the knife edge 39 and the loop portion 43, and hence the toggle member is disposed overcenter toward the right, this overcenter positioning being assisted by the spring 58. Normal operation of the refrigerating system is discontinued by the shifting of the toggle member 21 to the position shown in Fig. 2 since the downward movement of the part I of the operating arm 8 to the refrigeration-starting position is positively prevented, In order to remove this blocking force of the toggle member 21 when the temperature of the evaporator has reached a predetermined abnormally high value which insures completion of defrosting thereof, the trip arm 25 is provided for engaging a leg 52 of the lower pivoted element 31 of the toggle member 21. The trip arm 26 is pivotally mounted in engagement with the part 9 of the operating arm 5, this engagement being effected at a knife edge 53 at the end of the trip arm 26. The bellows 2.5 is arranged in engagement with a recessed portion 54 of the trip arm 26, and the expansive force of the bellows resulting from the increase in temperature of the evaporator is exerted upwardly against the trip arm 25. The upward movement of the bellows under defrosting conditions is opposed by a defrosting spring 55. One end of the spring 55 is arranged in engagement with the part 9 of the operating arm B and the other end engages a cup 56. The opposing force exerted by the spring 55 is adjusted by a screw 51 which engages the cup 55 and is in threaded engagement with an opening in the trip arm 25.

The upward movement of the part 9 of the operating arm 8, that is, the movement of the operating arm in the refrigeration-starting position is limited by a stop 55 bent from the bracket i5. Movement of the trip arm 26 away from the part of the operating arm B is limited by a stop 550,. As the temperature of the evaporator rises above the normal maximum temperature toward the abnormally high maximum defrosting temperature, further movement of the part 9 of the operating arm 2 and further compression of the spring 22 are prevented by the stop 58. Accordingly, the increased expansion of the bellows moves the trip arm away from the stop 58a. and upwardly against only the bias of the spring 55. It will be noted, therefore, that the abnormally high maXimum defrosting temperature setting, as established by the adjusting screw 51, is independent of the adjustment of the spring 22 which determines the normal maximum and minimum temperatures.

The broad idea of a control including two arms, a normal biasing spring engaging one arm and a defrost spring between the arms, and including a stop engaging the one for rendering the normal biasing spring ineffective so as to make the defrost temperature independent of the normal temperature setting is not part of the present invention but is described and claimed in my copending application, Serial No. 203,166, filed December 28, 1950, now Patent No. 2,627,561, issued February 3, 1953, and assigned to the same assignee as the present invention.

Ultimately, the trip arm '26 reaches a position wherein the end thereof engages the leg 52 of the lower pivoted element 31 of the toggle member 21. Further upward movement of the trip arm 26 then pivots this lower element 31 in a -counterclockwise direction, moving the knuckle 38 overcenter to the left with respect to the knife edge 39 and the loop portion 43, as shown in Fig. 3, breaking the toggle member 21. This removes the blocking effect of the toggle member 21 to the downward movement of part |0 of the operating arm 8. The part I0 of the operating arm then snaps downwardly overcenter to open the valve and start refrigeration, terminating the defrost period. The aforementioned breaking of the toggle member 21 effects movement of the tongue 4| out of the recess 5| of the cam 28, because part of the energy stored in spring is transferred to toggle member 21 and causes it to move rapidly to the left, thereby freeing itself from flange 48. Since the cam 28 is not advanced further until there is an upward snap action movement of the part I6 of the operating arm 8 at the start of the refrigerating portion of the next normal operating cycle, the recess 5| still remains in substantial alignment with the tongue 4|. Accordingly, in the absence of special provision, the tongue 4| could re-enter the recess 5| when the bellows 29 had contracted sufficiently to move the trip arm 26 downwardly out of engagement with the leg 52 of the lower pivoted element 31. In order to prevent such undesired re-entry of the tongue 4| into the recess 5|, a resilient element 59 is provided. The resilient element 59 is mounted on the shaft of the cam 29 and includes a portion 65 disposed in the general region of the periphery of the cam 25 immediately adjacent the recess 5I. As the cam 28 is advanced toward the defrosting position shown in Fig. 2, the resilient element 59 is engaged by the tongue 4| at the portion 6| which projects slightly beyond the periphery 42 of the cam 28, and the resilient element 59 is forced in a clockwise direction beyond the edge 62 of the recess 5i, affording space for entry of the tongue 4| into the recess 5| to initiate the de irosting period. When the tongue 4| is withdrawn from the recess 5| at the termination of the defrosting period, the resilient member 59. moves counterclockwise to resume its original position, as shown in Fig. 4, blocking re-entry of the tongue 4| into the recess 5|.

In the modified form shown in Fig. 5 a single pivoted interfering member 53 is substituted for the toggle member 21 for blocking the movement of the part |0 of the operating arm 8. The member 63 is pivoted at 64 and includes a leg 65 corresponding to the leg 52 of the form previously described. The member 63 further includes a tongue 66 corresponding to the tongue 4| in the form of invention shown in Figs. 1 to 4 inclusive. ,The member 153 is biased against the cam or disk 28 by a spring 48. In order to reduce the friction and minimize variations in the operation of the device, a roller lil' is mounted on a pin 68 at the upper end of the member S3. The roller 6l is adapted to engage the depending flange Ml on the operating arm t. The trip arm 2li is arranged to engage the leg 65 for swinging the member 63 countercloclrwise out of its blocking position after a predetermined abnormally high temperature has been reached during the defrosting period.

The operation of the device shown in Fig. is essentially the same as that of the form of control previously described. When the recess 5| is moved into alignment with the tongue 66, the pivoted member E3 swings into the position shown in Fig. 5, the position of the member 63 being established by the biasing spring i8 and the engagement of the end of the tongue G6 with the bottom of the recess 5i. In this position the member t3 is arranged to engage the lower end of the flange il@ and to block downward movement of the part lil of the operating arm 3 to the refrigeratiomstarting position. Under these conditions, a further expansion of the bellows 20 is required to move the trip arm upwardly against the bias of the spring as in the form illustrated in i.. Ultimately, the expansion of the bellows moves the end of the trip arm 26 into engagement with the leg 55 of the pivoted member Ilili, swinging this member ceunterclockwise and moving the roller 6l from beneath the lower end of the flange lill. This permits the part I0 of the operating arm to move downwardly, terminating the defrost period and initiating refrigeration. In the event that a greater error resulting from variations in friction can be tolerated, the roller 6l' can be omitted, the solid upper end of the pivoted member t3 then directly engaging the flange While I have shown and described specific em-V koperating arm movable between two positions for Starting and stopping refrigeration at predetermined maximuin minimum temperatures, a temperature-responsive element for effecting movement of said arm, a biasing spring engaging arm for opposing said element, a pivoted interfering member movable between a rst position wherein member acts as a stop for said arm and a second position wherein said member does not obstruct movement of said arm, said member including a roller at one end thereof for engaging said arm, cam engaging said member for affording movement of said member between `First and second positions, and means actuatei at a predetermined abnormally high maximum temperature for shifting said member from said rs position to said second position to terminate opposition by said member to movement oi said arm.

2. A refrigerator control comprising a pivoted operating arm movable between two positions for starting and stopping refrigeration at predetermined maximum and minimum tempera tures, a temperature-responsive element for effecting movement of said arm, a biasing spring engaging said arm for opposing said element, a toggle member movable between a first position wherein said toggle member acts as a'stop for Vsaid y,arm and a second position wherein said toggle member does not obstruct movement of said arm, a cam engaging said toggle member for affording movement or" said toggle member between said first and second positions, and a pivoted trip arm for engaging said toggle member at a predetermined abnormally high maximum temperature `when said toggle member is in lsaid .rst position for breaking said toggle member to terminate opposition by said toggle member to movement of said arm.

3. A refrigerator control comprising a pivoted operating arm movable between two positions for starting and stopping refrigeration at predetermined maximum and minimum temperatures, a temperature-responsive element for effecting movement of said arm, a biasing spring engaging said arm for opposing said element, a toggle member movable between a first position wherein said toggle member acts as a sto-p for said arm and a second position wherein said toggle member does not obstruct movement of said arm, a cam,

a spring for biasing said toggle member overcenter in one direction against said cam, said cam affording movement of said toggle member between said first and second positions, and means actuated at a predetermined abnormally high maximum temperature when said toggle member is in said first position for shifting said toggle member overcenter in the opposite direction to terminate opposition by said toggle member to movement of said arm.

4;. A refrigerator control comprising a pivoted operating arm movable between two positions for Starting and stopping refrigeration at predetermined maximum and minimum temperatures, a temperature-responsive element for eiecting movement of said arm, a biasing spring engaging said arm for opposing said element, a toggle member movable between a first position wherein said toggle member acts as a stop for said arm and a second position wherein said toggle member does not obstruct movement of said arm, said toggle member including two pivoted elements, a cam, a spring for biasing one of said pivoted elements against said cam and for biasing said toggle member overcenter in one direction, said cam affording movement of said toggle member between said first position and second posit-ion, and a pivoted trip arm for engaging the other of said pivoted elements of said toggle member to shift said toggle member overcenter in the opposite direction for terminating opposition by said toggle member to movement of said arm.

5. A refrigerator control comprising a pivoted operating arm movable between two positions for starting and stopping refrigeration at predetermined maximum and minimum temperatures, a temperature-responsive element for ellecting movement of said arm, a biasing spring engaging said arm lfor opposing said element, a toggle member movable between a rst position wherein said toggle member acts as a stop for said arm and a second position wherein said toggle member does not obstruct movement of said arm, a rotatable cam including a recess therein, said toggle member including a tongue for engaging said cam, said cani being rotatable to position said recess in alignment with said tongue to afford movement of said toggle member into said iirst position, a resilient element adjacent said recess to block entry of said tongue thereinto, said tongue engaging said resilient element at one point in the rotation of said cam to move said resilient element for at least partially removing blockage of said recess, and means actuated at a predetermined abnormally high maximum temperature when said toggle member is in said first position for breaking said toggle member to terminate opposition by said toggle member to movement of said arm.

6. A refrigerator control comprising a pivoted operating arm movable between two positions for starting and stopping refrigeration at predetermined maximum and minimum temperatures, a temperature-responsive element for effecting movement of said arm, a biasing spring engaging said arm for opposing said element, a pivoted member movable between a iirst position wherein said pivoted member acts as a stop for said arm and a second position wherein said pivoted member does not obstruct movement of said arm, a rotatable cam including a recess therein, said pivoted member including a tongue for engaging said cam, a spring for biasing said tongue against said cam, said cam being' rotatable to position said recess in alignment with said tongue to afford movement of said pivoted member into said rst position, a resilient element adjacent said recess to block entry oi said tongue thereinto, said tongue engaging said resilient element at one point in the rotation of said cam to move said resilient element for at least partially removing blockage oi said recess, and means actuated at a predetermined abnormally high maximum temperature for moving said pivoted member from said first position to said second position to terminate opposition by said pivoted member to movement of said arm.

'7. A refrigerator control comprising a pivoted operating arm movable between two positions for starting and stopping refrigeration at predetermined maximum and minimum temperatures, a temperature-responsive element for effecting movement of said arm, a biasing spring engaging said arm for opposing said element, a toggle member movable between a first position -wherein said toggle member acts as a stop for said arm and a second position wherein said toggle member does not obstruct movement of s-aid arm, a rotatable disk engaging said toggle member for eifecting movement of said toggle member between said first and second positions, said disk including a recess in the periphery thereof, said toggle member including a tongue engaging the periphery of said disk, a ratchet, a pawl mounted on s-aid operating arm and engaging said ratchet for advancing said ratchet each time said operating arm is moved between stopping and starting positions, gear means lbetween said ratchet and said disk for effecting rotation of said disk upon movement of said ratchet, means dependent upon a predetermined number of actuations of said ratchet for positioning said recess in alignment with said tongue to afford movement of said toggle member to said rst position, and a pivoted trip arm for engaging said toggle member at a predetermined abnormally high maximum temperature when said toggle member is in said iirst position for breaking said toggle member to terminate opposition by said toggle member to movement of said arm.

8. A refrigerator control comprising a pivoted two-part operating arm including a first part and a second part, an overcenter spring between said parts for effecting relative snap action movement of said parts, a temperature-responsive element for effecting movement of said rst part of said arm, a biasing spring engaging said first part of said arm for opposing said temperatureresponsive element, a stop for engaging said second part of said arm for opposing movement of said operating arm to its refrigeration-starting position, said stop -comprising a toggle member movable between a first position wherein said toggle member blocks movement of said operating arm to its refrigerant-starting position and a second position wherein said toggle member does not obstruct movement of said operating arm, a cam engaging said toggle member for affording movement of said toggle member between said first and second positions, and means actuated at a predetermined abnormally high maximum temperature when said toggle member is in said rst position for breaking said toggle member to terminate opposition by said toggle member to movement of said arm.

9. A refrigerator control comprising a pivoted two-part operating arm including a first part and a second part, an overcenter spring between said parts for eifecting relative snap action movement of said parts, a temperature-responsive element for effecting movement of said rst part of said arm, a biasing spring engaging said rst part of said arm for opposing said temperatureresponsive element, a Stop for yengaging said second part of said arm for opposing movement of said operating arm to its reirigeration-starting. position, said stop comprising a toggle member movable between a rst position wherein said toggle member blocks movement of said operating arm to its refrigerant-starting position and a second position wherein said toggle member does not obstruct movement of said operating arm, said toggle member including two pivoted elements, a cam, a spring for biasing one of said pivoted elements against said cam and for biasing said toggle member overcenter in one direction, said cam affording movement of said toggle member between said first position and second position, and a pivoted trip arm for engaging the other of said pivoted elements of said toggle member to shift said toggle member overcenter in the opposite direction for terminating opposition by said toggle member to movement of said arm.

10. A refrigerator control comprising a pivoted two-part operating arm including a rst part and a second part, an overcenter spring between said Parts for effecting relative snap action movement of said parts, a temperature-responsive element for effecting movement of said first part of said arm, la biasing spring engaging said first part of said arm for opposing said temperatureresponsive element, a stop for engaging said second part of said arm for opposing movement of said operating arm to its refrigeration-starting position, said stop comprising a toggle member movable between a iirst position wherein said toggle member blocks movement oi said operating arm to its refrigeration-starting position and a second position wherein said toggle member does not obstruct movement of said operating arm, said toggle member including two pivoted elements, a rotatable disk, one of said vpivoted elements of said toggle member including a tongue adapted to engage the periphery of said disk, a spring for biasing said tongue against said periphery of said disk and for biasing said toggle overcenter in one direction, said disk including a recess in the periphery thereof, a ratchet, a lpawl mounted on said operating arm and engaging said ratchet for advancing said ratchet each time said operating arm is moved between stopping and starting positions, gear means between said ratchet land said disk for effecting rotation of said disk upon movement of said ratchet, means dependent upon a predetermined number ci' actuations of said ratchet for positioning said recess in alignment with said gear to afford movement of said toggle member to said first position, and a pivoted trip arm for engaging said toggle member at a predetermined abnormally high maximum temperature when said toggle member is in said rst position for breaking said toggle member to terminate opposition by said toggle member to movement of said arm.

.1.1. A refrigerator control comprising a pivoted two-part operating arm including e, iirst part and a second part, an overcenter spring between said parts for effecting relative snap action movement of said parts for starting and stopping refrigeration at predetermined maximum and minimum temperatures, a temperature-responsive element for effecting movement of said first part of said arm, a first biasing spring engaging said iirst part of said arm for opposing said temperature-responsive element, means for adjusting said spring to vary said maximum and minimum temperatures, a stop for engaging said iirst part of said operating arm to limit movement of said rst part in a refrigeration-starting direction, a toggle member movable between a rst position wherein said toggle member acts asa stop for blocking movement of said arm to its refrigera tion-starting position and a second position wherein said toggle member does not obstruct movement of said arm, a cam engaging said'toggle member for aording movement of said toggie member between said first and second positions, means actuated at a predetermined abnormally high maximum temperature when said toggle member is in said rst position for breaking said toggle member to terminate opposition by said toggle member to movement or said arm, a second spring for opposing movement of said temperature-responsive element when said toggle member is in said rst position, and means for adjusting said second spring to vary said ab? normally high maximum temperature independently of the variations in maximum and minimum temperatures effected by adjustment of said rst spring.

12. A refrigerator control comprising a pivoted operating arm movable between two positions for starting and stopping refrigeration at predctermined maximum and minimum temperatures, a temperature-responsive element for eiecting movement of said arm, a biasing spring engaging said arm for opposing said element, a toggle member movable between a first position wherein said toggle member acts as a stop for said arm and a second position wherein said toggle member does not obstruct movement of said arm, said toggle member including two pivoted elements, a cam, a spring for biasing one of said pivoted elements against said cam and for biasing said toggle member overcenter in one diretion, the other of said pivoted elements including a portion engaging said one of said pivoted elements to limit the amount of overcenter movement of said toggie members in said one direction, said cam affording movement of said toggle member between said first position and` second position, and a pivoted trip arm for engaging said other of said pivo'teol elements of said toggle member to shift said toggle member ovcrcenter in the opposite direction for terminating opposi tion by said toggle member to movement of said arm.

CHARLES S. GRIMSHAW.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,867,711 Raney July 19, 1932 1,933,580 Bauer Nov. 7, 1933 1,969,304 Grooms Aug. 7, 1234 1,979,103 Gaynor Oct. 30, 1934 2,366,635 McCloy Jan. 2, 1945 2,459,083 McCloy Jan. 11,. 1949 2,627,561 Grimshaw Feb. 3. 1952 

